At present, certain telephony systems comprise: (a) telephone switching machines such as digital switching machines--one example of such telephone digital switching machines being a computerized business exchange (CBX) manufactured by ROLM Systems of Santa Clara, Calif.; (b) subscriber telephone sets--one example of such subscriber telephone sets being a ROLMPhone digital subscriber telephone set manufactured by ROLM Systems; and (c) telephone lines which connect the subscriber telephone sets to the digital switching machines--one example of such telephone lines being a ROLMLink twisted pair of wires. In particular, in a telephony system wherein the digital switching machine is a CBX, a ROLMLink interface (RLI) card is used to interface several individual telephone lines with the CBX.
FIG. 1 shows a block diagram of a portion of the telephony system referred to above wherein RLI 110 interfaces ROLMLink 120 with CBX 100. In the embodiment shown in FIG. 1, ROLMLink 120 comprises a twisted pair of wires which connects RLI 110 to a distributing frame (not shown) and a twisted pair of wires which connects the distributing frame to ROLMPhone 140.
It is well known in the art that there is a need to detect the presence of troubles which occur in communications between CBX 100 and ROLMPhone 140 and, thereafter, to sectionalize automatically, i.e., to determine the location of such troubles. Presently available telephony systems fall short of satisfying the need to detect the presence of troubles because, in general, they do not have the capability to detect troubles automatically. In fact, in such presently available telephony systems, troubles are detected typically by users who have detected unsatisfactory communications when they have attempted to use the system. Additionally, presently available telephony systems fall short of satisfying the need to sectionalize troubles automatically once the troubles have been detected. In particular, such telephony systems cannot determine automatically whether the trouble exists in ROLMPhone 140 or in the telephone line connecting ROLMPhone 140 and CBX 100, which telephone line is comprised of ROLMLink 120.
As is well known to those of ordinary skill in the art, it is important to sectionalize troubles in order to direct a repair person to the part of the communications link in which a trouble exists. In addition, if the telephone line has discontinuities or other defects that could affect transmission it would be very useful to determine the approximate distance from the switching machine to the defect.
At present, sectionalization of troubles is performed as follows. ROLMPhone 140 is disconnected manually from ROLMLink 120 and a reflectometer is connected manually to ROLMLink 120 in its place. In operation, the reflectometer sends a pulse towards CBX 100 and the reflectometer displays the reflection of that pulse, i.e., the echo, on a visual display such as, for example, an oscilloscope display. The echo is then interpreted, in a manner which is well known to those of ordinary skill in the art, to determine whether a problem exists in the connection between the end of ROLMLink 120 and CBX 100. As one can readily appreciate, the described sectionalization procedure is time consuming, expensive, and is typically performed after a user's dissatisfaction with service has prompted him or her to report a trouble.
As a result of the above, there is a need for method and apparatus for detecting and sectionalizing troubles on telephone lines automatically.